This application proposes to study the regulation of Rev shuttling and localization. We seek to determine how the rates of import and export of Rev are modulated by the cellular environment. We will gain insights into this process by seeking to understand why a single Rev NES functions inefficiently and why the nuclear localization of Rev is sensitive to the inhibition of transcription and exposure to oxidative stress. Preliminary studies show that Vpr can shuttle between the nucleus and cytoplasm. This observation indicates that Vpr is Rev-like because it contains both a nuclear import and a nuclear export signal. This proposal will compare the shuttling of Vpr to that of Rev and determine if their export is mediated by the same cellular factors. The studies will also identify and characterize the NES in Vpr. The long-term objective is to understand the molecular details of HIV Rev action and Vpr shuttling. Defining the details of the regulation of Rev import and export and the export of Vpr will lead to a better understanding of the interactions between these proteins and endogenous transport pathways. This basic knowledge may lay the groundwork for novel therapeutic approaches targeting Rev function.